1. Field of the Invention
This invention relates to an apparatus, preferably a truck-carried apparatus, for pumping concrete through a casting tube to a casting zone, said apparatus being in particular studied and constructed for operating at very low environmental temperatures, below 0.degree. C. and down to -40.degree. C.
2. Description of the Prior Art
A pumping apparatus of this type essentially consist of a pumping group, preferably a multicylinder type with distributing valves, and driven by its own engine. The pump receives the concrete from a charging hopper and conveys the same into a casting tube formed of several lengths connected and sustained by an articulated arm whose position can be adjusted at will. Besides these fundamental components, different devices are provided for accessory tasks and operations, as will be seen hereinafter.
The use of similar apparatuses in environments characterized by low and very low temperatures is, as it may be guessed, subject to a series of noteworthy problems which have not yet been solved and which are essentially caused by the necessity of bringing to and keeping the major part of the components of the apparatus within well stated temperature ranges, of constantly checking these conditions and obviously assuring in the meantime the perfect operation of all apparatus components in each foreseen operating phase.
In particular, all the apparatus parts coming into contact with the concrete shall be brought to and maintained at a temperature which is superior to 0.degree. C. and less than 30.degree. C., while other mechanical parts shall be preheated or heated to avoid excessive thermal stresses which might cause their breaking. It is evident that it is not convenient nor thinkable to ensure the heating of all these components and in particular that of those having a considerable thermal mass and inertia, such as the pumping and hopper groups, using for this purpose conventional systems of the electric resistance type, because of the excessive loads these systems would involve for the power generators of the apparatus.